Shear pins are well known in the art and are often used in applications where excessive and unusual constraints applied to a component of machinery can be dangerous for health and safety reasons, or may cause expensive machinery components to be permanently damaged. In these circumstances, a shear pin is used to provide a predetermined level of resistance to shear stress, and when that level is exceeded by an abnormal condition, the shear pin breaks at a predetermined location, warning a technician in some way and thus protecting an operator or a more expensive component.
In the field of hydroelectric power plants, for example, turbines are equipped with wicket gates that control the quantity of water allowed inside. The transmission of movement from a driving component to the wicket gate is done via a shear pin. In the advent of a foreign object jamming inside the gate, the excessive force transmitted to the shear pin will result in the breakage of a shear pin. The wicket gate will no longer be driven and will not be damaged.
Given their very nature, shear pins are expected to break in certain conditions and must thereafter be replaced. In certain applications, shear pins are disposed in hard-to-reach areas, and although the top of the shear pin are sometimes visible, it is remains difficult to tell if they are broken or not. Disassembling machinery components to verify if a shear pin is broken or not can be quite time consuming. Further, when many shear pins are provided on a piece of machinery, it is not always obvious which particular shear pin has broken and much time is lost inspecting the piece of machinery to find the broken one. Thus, there remains a need for an indication of shear pin breakage either visually accessible at the visual portion of shear pins, or accessible at a remote location from them.
Some detection devices have been provided in the past, but most are electrical and resistor based. Wires exiting shear pins and connecting them to a receiver circuitry are cumbersome, especially when many shear pins are used.